Oculodentodigital syndrome (ODDD) is a rare autosomal dominantly inherited syndrome characterized by developmental and morphogenetic abnormalities (e.g., syndactyly, craniofacial anomalies, dental enamel hypoplasia, etc.), glaucoma, and a slowly progressive spastic paraparesis. We have utilized the resources of the GCRC to recruit multiple large families with ODDD and to perform linkage analysis to map the gene(s) for the disorder. To date we have ascertained seven multiplex families from the United States, Canada, and Norway comprising a total of 57 potentially informative meioses. Dr. Robert Shapiro has performed physical examinations on more than 70% of these individuals to confirm their phenotype. One observation which emerged from these analyses is that the severity of the age of onset of the spastic paraparesis appear to follow the pattern of trait expression known as genetic anticipation; that is, greater phenotypic severity and/or the age of onset of inherited traits may occur in successive generations. Comparable to known genes for several other diseases with anticipation, this phenotypic inheritance pattern suggests that presence of a trinucleotide repeat expansion in the gene responsible for the disease.